Abstract
Ionic complexes consisting of a mesogenic cholesterol derivative and 1-alkyl (Cn)-3-methylimidazolium (CnMim) (n = 6–18) were prepared from ethanol solutions containing an equimolar mixture of cholesterol hydrogen phthalate (CHP) and 1-Cn-3-methylimidazolium hydroxide; the imidazolium hydroxide was obtained by anion exchange of 1-Cn-3-methylimidazolium bromide. The complex samples, termed [CnMim][CHP], were examined to evaluate their thermal transition patterns. Excluding the two samples (n = 6, 8) that showed no definite ordered phase, the complexes with n ≥ 10 formed a cholesteric (n = 10, 12) or smectic (n = 14–18) mesophase in a considerably wide range of temperatures; this wide range reflects the additional thermotropic property of the salts of CnMim with longer alkyl chains. These fluid mesophases transformed into a mesomorphic vitreous solid without crystallization in a usual cooling process. For the glassy mesomorphic samples of selected complexes (n = 10, 18), the enthalpy relaxation behavior was followed as a function of the aging temperature and time, and the data were analyzed in terms of a Kohlrausch–Williams–Watts (KWW) type of stretched exponential equation. A very narrow distribution of relaxation times was observed for the “liquid crystalline glasses”, indicating the high uniformity of the relaxation mode.
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This work was partially financed by a Grant-in-Aid for Scientific Research (A) (No. 26252025 to YN) from the Japan Society for the Promotion of Science.
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Nakajima, I., Kitaguchi, T., Sugimura, K. et al. Mesomorphic glass-forming ionic complexes composed of a cholesterol phthalate and 1-Cn-3-methylimidazolium: phase transition and enthalpy relaxation behavior. Polym J 50, 899–909 (2018). https://doi.org/10.1038/s41428-018-0047-5
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DOI: https://doi.org/10.1038/s41428-018-0047-5
